Hoping for some advice on using henna over existing highlights please! For the past couple of years I’ve had chestnut/caramel highlights in my naturally dark brown hair to lift the colour a bit and distract from the greys. However I can’t really justify the regular expense anymore, my hair is suffering with the bleach despite having used Olaplex (it’s quite thin hair at the best of times) and I’d like to start using something more natural. I’ve been thinking about trying Lush’s caca brun, but is it a bad idea to use henna over highlights like these? Hugely grateful for any tips!